Experimental studies of Rio Grande virus in rodent hosts.

Rio Grande (RG) virus, a new member of the Phlebotomus fever serogroup, was inoculated into wild wood rats (Neotoma micropus) and laboratory-reared cotton rats (Sigmodon hispidus) to determine if these potential hosts could be experimentally infected. Nine of 14 (64%) wood rats became viremic, with titers of circulating virus ranging from 10(2.3) to 10(5.3) plaque-forming units (PFU)/ml and a geometric mean titer of 10(3.7) PFU/ml. Virus was not detected in urine specimens from inoculated wood rats but was found in a single saliva specimen. RG virus was detected in the blood of 1 of 12 (8%) cotton rats. Neutralizing (N) antibody developed in 8 of 9 inoculated wood rats which survived for 30 days postinoculation and in 11 of 12 cotton rats. N antibody was still detectable in 4 of 7 wood rats which survived for 1 year, and all 7 were resistant to rechallenge with the virus, as were 3 wood rats with naturally-acquired antibody. High mortality (36%) occurred in inoculated wood rats; whereas low mortality (8%) occurred in cotton rats. The specific cause of death of the rats was not determined. Modes of transmission of the virus in nature are discussed.

Rio Grande--a new phlebotomus fever group virus from south Texas.

Three strains of a new Phlebotomus fever group virus were isolated from pack rats (Neotoma micropus) collected in south Texas during 1973--1974; the name Rio Grande was proposed for this virus. The virus is pH 3.0 labile, sensitive to the action of sodium deoxycholate and heat (56 degrees C) labile. The results of a serosurvey indicated that pack rats are probably the principal vertebrate host for Rio Grande virus and that year-round transmission of the virus may occur. Because no isolations of this virus were made from hematophagous insects, the vector, if any, remains undetermined.